Table 3.
Previous measurements of the time delay Δt and the differential magnification ℛq between the NE and SW lensed images.
| Observations date | Method | Δt (days) | ℛq | Note |
|---|---|---|---|---|
| 1990–1991 | Light-curve of VLA data at 8.4 and 15 GHz | 44 ± 9 (a) | 1.17 − 1.23 | van Ommen et al. (1995) |
| 1997–1998 | Light-curve of ATCA 8.6 GHz data |
 |
1.52 ± 0.05 | Lovell et al. (1998) |
| 1996–1998 | Saturation of the HCO+J = 2 − 1 line |
 |
– | Wiklind & Combes (2001) |
| 1997 Jan.–Apr. | 43 GHz VLBI observations (b) | – | 1.13 ± 0.61 | Jin et al. (2003) |
| 2008–2010 | γ-ray light curve from Fermi-LAT | 27 ± 0.6 (c) | – | Barnacka et al. (2011) |
| 2012 Apr.–Jun. | Model of a chromatic jet to ALMA data | 27 (d) | 1.35 | Martí-Vidal et al. (2013) |
| 2008–2015 | γ-ray light curve from Fermi-LAT | 23 ± 0.5, 19.7 ± 1.2 (e) | n.c. (e) | Barnacka et al. (2015) |
| 2008–2011 | γ-ray light curve from Fermi-LAT | n.a. (e) | > 6 (e) | Abdo et al. (2015) |
| 2019 Jul. | Lensing model from ALMA observations | 26–29 (f) | 1.07 (d) | Muller et al. (2020a) |
| 2016 Mar.–Sep. | ALMA monitoring | 25 ± 3 (g) | 1.24 ± 0.04 (g) | This work |
Notes.
From the determinant of the relative magnification matrix between the two vectors formed by the core-jet separation and offset between polarized and total-intensity emission for different epochs;
Disputed by Abdo et al. (2015), as signal in the time-series analysis could come from the Moon’s orbital motion;
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